A Question on the Quality of Surly Bikes: Is It Worth It?

I'm looking into buying a Surly as a 2nd bike (1st is gravel). I'd like to be able to take it on rocky, muddy and sandy terrain, while still being decent on tar. But the real consideration is that the parts be durable and repairable for crossing Africa (I may even turn it into a world trip). What advice do you have for parts given the above? I'm thinking of wider tyres without suspension, but not sure how wide to go. Jones bar? What drivetrain? I've heard of Rohloff-like systems, but am concerned about repairs in remote areas. Anything else to consider?

I have been using Surly's for more than 100 000 km on any kind of road or track. My advice is to go to the disk trucker (the LHT is reliable but lacks rigidity, which is sometimes unpleasant). I use Shimano Deore XT, but the Deore std is good too and cheaper. With the discs and mechanical pads, the hydraulic ones are too difficult to fix if damaged. Good rims with 36 spokes, I use Ryde big bull, with 26x1,75 Schwalbe marathon touring plus.
The disk trucker appears to be designed more for tar. I have 2" tyres on my gravel bike, and feel like I should go wider for this next bike given what I end up travelling on. I've heard about going 26" from several people, so definitely heeding that advice. The current bike is 36 spokes and mechanical disc brakes, so agree there too.
26" is better if you go to remote countries, central Asia... for the availability of spare tyres. You can go up to 2,25" tyres if you wish, but remember that you will do very likely mainly tar roads, and 29" rims if you are more than 6'. The Surly can go anywhere!
where have you ridden those huge distances? Africa and other remote countries?
in fact, 200 000 km in the last 12 years, but only the last 100 000 km on Surly's. RTW of 110 000 km and 5,5 years, and 2 trips/year since Paraguay, Madagascar, Ivory Coast, south-east Asia, Pamir, Yunan and Vietnam, Kamchatka, North Cape for the main ones.
any suggestions of where you'd most recommend on a world trip? I have Africa largely planned, just starting to look into how I might approach the Americas. I'm considering the GDMBR for NA. Very little idea as to how to tackle South America.
I don't use it, so don't do recommendations on the itinerary. Personally, I just dream on a big map of the world that I have on the wall of my bedroom, then on paper maps during the trip. My personal taste is for remote areas and mountains, but for the latest, my age is starting to oblige me to reduce my ambitions 😡. On a trip from Vancouver to Mexico, you will find plenty of options of "off roads" for instance. In the Americas, the most impressive landscapes are on the west side. In Africa, don't miss Ethiopia and Namibia. But Cameroun and Egypt, depending on which side of Africa you choose, are worth the visit. Don't prepare too much. Personally, I concentrate on the weather and on safety and administrative limitations (wars, visas...), then go.
small correction: if I don't spend much time preparing the trip itself, I do spend time preparing the equipment. I hate losing time, energy and money because of failing and inappropriate equipment!
I'm somewhat the same, just to have some idea of the area in going through like a little history of the local people. But once in a place, I make routing decisions a couple of days ahead.
I did some research, I'm leaning towards the ogre. Have you ever used it?
surly ogre. 
no, only an LHT, and now a disk trucker. I just checked the ogre. The frame is fine but not for 26" wheels.
I looked too. I like the 1x gearing for simplicity. 
narrower chain, misaligned most of the time, lasting? Availability in remote countries of the spares? Never had a failure on the chainrings, just changing them and the cable every 30000 km.
Rohloff and belt drive order parts your using or gonna be using double like belt and front and rear cogs 2x let someone send them to you about 15.000 miles through then swap it typical belt drive does about 30.000 miles per belt depending on the usage/terrain YMMV. you can also just swap out the rear cog after 15k since that's the part which wears down the fastest get some nice fat tyres no skinny ones so like c47 or c50 650b wheelset with Rohloff they last really long people have clocked over 300.000 miles on the easy.
so you're saying you can comfortably tour with Rohloff? Is it easy to replace yourself? Easy to tell when it's about due for replacement? I have little knowledge of it besides that it's easy to run compared to a regular chain.
Rohloff can't be fixed on the road. They have a good after-sale service, but you have to wait for the replacement to arrive. I have met people having broken it at 30 000 km. Belts are longer lasting than chains, don't need maintenance, but don't like dust, mud or sand, and you won't find spares outside Europe, USA..., and even in these countries, not everywhere.
you can send your whole wheel or just the hub for maintenance to Rohloff if you have big issues which I have had none only need to replace the oil in the hub about every 5000km I do it every 3000 just to endure the life of the Rohloff overall yes its easy to spot when u need to change the cogs out since the "teeth" on the cogs of belt drive are wide and flat if they get narrow and sharp they can cut through the belt that's usually the point you swap everything out send the rest home and you can use the worn parts for local touring as I did so they don't go to waste oil change can be done by yourself too if you know how and got the tools, of course, I carry an oil change set anyway cause I use hydraulic disc brakes to with 4 pistons
have had 0 issues with sand mud etc on my belt or cogs use the cdx system, not the cheap cdn system the only thing belts don't like is lava mud which cakes on and stays on haha only issue I've ever had also seen people get a leaky seal so the oil would run out on some Rohloff he sent his wheel and 3 weeks later got it back he had an extra wheel trailer with a whole complete wheel with spare Rohloff ready to go just in case something like that would ever happen
Get the simple and cheap components and gear, parts you can replace or fix in most places around the world.
I don't know what those are though.
All materials are as simple as possible.
I rode a surly troll from Sudan to Cape Town then Ushuaia to Prudhoe Bay Alaska. An awesome bike that took an absolute beating on some of the worst roads you could imagine. The frame did snap in Argentina but got it brazed. It lasted until Canada and had it welded but only lasted a week. I then welded it myself and put a clamp on it and is still going. I had standard rim brakes but would recommend discs. I ran a Rohloff hub gear and although had a couple of issues the backup service from Rohloff was second to none and looking at the terrain and weight I carried it was perfect for the job. The one thing I would do is change the ridged forks for suspension forks.
troll is discontinued. Ogre is the closest and that's what I'm looking to get. You mention suspension. Most people say not to get it as it's an extra part that can be hard to repair in remote regions. An option I've been considering is a shock-absorbing stem that can easily be replaced with a regular stem.
have you looked at Lauf forks?
very expensive, and it looks like it offers only 30mm of suspension. The redshift shock stop stem is much less and offers 20mm. I'm used to the stem system with my current specialized bike and find it works well e with a wider tyre.
it has 60mm of travel with no maintenance and cost the same as a good set of suspension forks but your bike your choice
I ride a Stevens with Pinion P 1-18. Nothing to repair.